Re: [Patch V5 2/3] tpm_tis-spi: Support hardware wait polling

Jarkko Sakkinen
2023-02-28T02:36:35Z

On Mon, Feb 27, 2023 at 05:37:01PM +0530, Krishna Yarlagadda wrote:
> TPM devices raise wait signal on last addr cycle. This can be detected
> by software driver by reading MISO line on same clock which requires
> full duplex support. In case of half duplex controllers wait detection
> has to be implemented in HW.
> Support hardware wait state detection by sending entire message and let
> controller handle flow control.

When a is started sentence with the word "support" it translates to "I'm
too lazy to write a proper and verbose description of the implementation"
:-)

It has some abstract ideas of the implementation, I give you that, but do
you think anyone ever will get any value of reading that honestly? A bit
more concrette description of the change helps e.g. when bisecting bugs.

> QSPI controller in Tegra236 & Tegra241 implement TPM wait polling.
>
> Signed-off-by: Krishna Yarlagadda <kyarlagadda@nvidia.com>
> ---
> drivers/char/tpm/tpm_tis_spi_main.c | 92 ++++++++++++++++++++++++++++-
> 1 file changed, 90 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm_tis_spi_main.c b/drivers/char/tpm/tpm_tis_spi_main.c
> index a0963a3e92bd..5f66448ee09e 100644
> --- a/drivers/char/tpm/tpm_tis_spi_main.c
> +++ b/drivers/char/tpm/tpm_tis_spi_main.c
> @@ -71,8 +71,74 @@ static int tpm_tis_spi_flow_control(struct tpm_tis_spi_phy *phy,
> return 0;
> }
>
> -int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
> - u8 *in, const u8 *out)
> +/*
> + * Half duplex controller with support for TPM wait state detection like
> + * Tegra241 need cmd, addr & data sent in single message to manage HW flow
> + * control. Each phase sent in different transfer for controller to idenity
> + * phase.
> + */
> +int tpm_tis_spi_hw_flow_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
> + u8 *in, const u8 *out)
> +{
> + struct tpm_tis_spi_phy *phy = to_tpm_tis_spi_phy(data);
> + struct spi_transfer spi_xfer[3];
> + struct spi_message m;
> + u8 transfer_len;
> + int ret;
> +
> + while (len) {
> + transfer_len = min_t(u16, len, MAX_SPI_FRAMESIZE);
> +
> + spi_message_init(&m);
> + phy->iobuf[0] = (in ? 0x80 : 0) | (transfer_len - 1);
> + phy->iobuf[1] = 0xd4;
> + phy->iobuf[2] = addr >> 8;
> + phy->iobuf[3] = addr;
> +
> + memset(&spi_xfer, 0, sizeof(spi_xfer));
> +
> + spi_xfer[0].tx_buf = phy->iobuf;
> + spi_xfer[0].len = 1;
> + spi_message_add_tail(&spi_xfer[0], &m);
> +
> + spi_xfer[1].tx_buf = phy->iobuf + 1;
> + spi_xfer[1].len = 3;
> + spi_message_add_tail(&spi_xfer[1], &m);
> +
> + if (out) {
> + spi_xfer[2].tx_buf = &phy->iobuf[4];
> + spi_xfer[2].rx_buf = NULL;
> + memcpy(&phy->iobuf[4], out, transfer_len);
> + out += transfer_len;
> + }
> +
> + if (in) {
> + spi_xfer[2].tx_buf = NULL;
> + spi_xfer[2].rx_buf = &phy->iobuf[4];
> + }
> +
> + spi_xfer[2].len = transfer_len;
> + spi_message_add_tail(&spi_xfer[2], &m);
> +
> + reinit_completion(&phy->ready);
> +
> + ret = spi_sync_locked(phy->spi_device, &m);
> + if (ret < 0)
> + return ret;
> +
> + if (in) {
> + memcpy(in, &phy->iobuf[4], transfer_len);
> + in += transfer_len;
> + }
> +
> + len -= transfer_len;
> + }
> +
> + return ret;
> +}
> +
> +int tpm_tis_spi_sw_flow_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
> + u8 *in, const u8 *out)
> {
> struct tpm_tis_spi_phy *phy = to_tpm_tis_spi_phy(data);
> int ret = 0;
> @@ -140,6 +206,28 @@ int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
> return ret;
> }
>
> +int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
> + u8 *in, const u8 *out)
> +{
> + struct tpm_tis_spi_phy *phy = to_tpm_tis_spi_phy(data);
> + struct spi_controller *ctlr = phy->spi_device->controller;
> +
> + /*
> + * TPM flow control over SPI requires full duplex support.
> + * Send entire message to a half duplex controller to handle
> + * wait polling in controller.
> + * Set TPM HW flow control flag..
> + */
> + if (ctlr->flags & SPI_CONTROLLER_HALF_DUPLEX) {
> + phy->spi_device->mode |= SPI_TPM_HW_FLOW;
> + return tpm_tis_spi_hw_flow_transfer(data, addr, len, in,
> + out);
> + } else {
> + return tpm_tis_spi_sw_flow_transfer(data, addr, len, in,
> + out);
> + }
> +}
> +
> static int tpm_tis_spi_read_bytes(struct tpm_tis_data *data, u32 addr,
> u16 len, u8 *result, enum tpm_tis_io_mode io_mode)
> {
> --
> 2.17.1
>

Looking pretty good but do you really want to export tpm_tis_spi_{hw,sw}_flow_transfer?

BR, Jarkko